Apparatus and process for testing uniformity of pulp

Abstract

An apparatus and process for testing the uniformity of a papermaking pulp with respect to the lignin associated with individual fibers comprising substantially simultaneous analysis of individual fiber length and fluorescence of the lignin associated with such individual fiber. The ratio of the lignin mass over the fiber length has been found to be proportional to the Kappa Number.

What is claimed is: 
     
       1. A process for determining the uniformity of papermaking pulp with respect to the lignin content associated with the fibers of said pulp comprising the steps of: selecting a sample of said pulp,   adjusting the concentration of fibers within said sample to a value less than about 100 milligrams of dry fiber to 1000 grams of water,   agitating said sample to disperse said fibers within said sample,   forming said sample into a flowing stream which includes individual fibers of said pulp suspended therein,   directing a beam of substantially monochromatic light into said stream to cause individual ones of said fibers moving through said beam to cast a length shadow and to cause lignin associated with individual ones of said fibers to fluoresce,   detecting said length shadow for individual ones of said fibers,   detecting the intensity of fluorescence of individual ones of said fibers,   correlating the length shadow value of a particular fiber with the fluorescence of the same fiber.   
     
     
       2. The process of claim 1 and including the step of computing the concentraton of lignin per unit of fiber length. 
     
     
       3. A process for testing the uniformity of pulp as respects the lignin content of the individual fibers thereof comprising the steps of: collecting a representative sample of said pulp,   adjusting the concentration of said sample to less than about 100 mg of dry fiber in 1000 g of water, forming said sample into a flowing stream having a cross-sectional dimension slightly greater than the cross-sectional dimension of individual ones of said fibers of said pulp such that individual ones of said fibers are caused to move length wise with the direction of flow of said stream,   directing a substantially monochromatic polarized beam of light into said stream at substantially a right angle to the direction of flow of said stream, said beam having a wave length of about 488 nm, whereby lignin associated with individual ones of said fibers is caused to fluoresce and individual fibers are caused to cast a length shadow,   capturing the length dimensions of the shadow of each fiber passing through said beam of light,   capturing the magnitude of the fluorescence of each fiber at a wave length of about 574 nm substantially simultaneously with the capture of its length dimension.   
     
     
       4. The process of claim 3 and including the step of converting said magnitude of fluorescence to a mass of lignin. 
     
     
       5. The process of claim 4 and including the steps electronically dividing the lignin mass value of each fiber by the captured length dimension of such fiber, and displaying the quotient so obtained. 
     
     
       6. A process for determining the uniformity of papermaking pulp with respect to the lignin content associated with the fibers of said pulp comprising the steps of: directing a substantially coherent beam of substantially monochromatic light into a flowing stream of said pulp containing discrete dispersed ones of said fibers, said beam of light having a wavelength suitable to fluoresce lignin,   detecting the magnitude of fluorescence of lignin associated with individual ones of said fibers.   
     
     
       7. The process of claim 6 including the further steps of: substantially simultaneously analyzing the length of said individual ones of said fibers, and   correlating said magnitude of fluorescence with said length of said individual ones of said fibers to provide a measure of the concentration of lignin associated with said individual ones of said fibers.   
     
     
       8. The apparatus of claim 6 wherein the wavelength of said beam of light incident upon said flowing stream is about 488 nm. 
     
     
       9. The apparatus of claim 8 wherein the wavelength of detected fluorescence is about 574 nm. 
     
     
       10. An apparatus for measuring the fluorescence and length of fibers that fluoresce the presence of light of at least one frequency, comprising: means defining a sample volume,   transport means for disposing individual ones of the fibers in the sample volume,   illuminating means for generating and directing a beam of light onto the sample volume and the fibers present within said sample volume,   said beam of light having at least one frequency that will cause the fibers to fluoresce at a fluorescent frequency,   first optical detector means for observing the fibers in said sample volume and for generating a length signal corresponding to the length of individual fibers in said sample volume;   second optical detector means disposed to receive fluorescent light produced by the fibers in said sample volume and for generating a fluorescence signal corresponding to the intensity of the fluorescent light from the fibers, and   processing means for receiving the length signal and the fluorescence signal and for producing a comparison signal corresponding to a comparison of the fluorescent light produced by the fiber to the length of the fiber.   
     
     
       11. The apparatus of claim 10 wherein said first optical detector is disposed to receive forward light scattering produced when the light beam strikes the fibers in said sample volume. 
     
     
       12. The apparatus of claim 10 wherein said second optical detector is disposed in a light path from said sample volume that is substantially perpendicular to the path of the beam of light from said illuminating means as it passes through said sample volume. 
     
     
       13. The apparatus of claim 10 wherein said means defining a sample volume comprises at least a capillary tube having a cross-sectional diameter that is within the range of 1.0 mm to 0.01 mm. 
     
     
       14. The apparatus of claim 10 wherein said processing means is a computer that compares the magnitude of the fluorescence signal to the length of the fibers. 
     
     
       15. Apparatus for determining the uniformity of papermaking pulp with respect to the concentration of lignin associated with the fibers of said pulp comprising: means containing a sample of said pulp including substantial numbers of discrete fibers dispersed in a liquid,   pump means,   conduit means leading from said sample containing means to said pump means for conveying said fibers from said sample containing means to said pump,   means defining a length of reduced cross-sectional area of said conduit interposed in the length thereof,   a source of substantially coherent and substantially monochromatic light incident upon said reduced cross-sectional area of said conduit,   said light being of a wavelength suitable to fluoresce lignin associated with said fibers moving through said conduit, and   means detecting the magnitude of fluorescence of lignin associated with individual fibers.   
     
     
       16. The apparatus of claim 15 including means detecting the shadow length of a fiber within said beam of light substantially simultaneously with the detection of fluorescence associated with such fiber, and means correlating said detected magnitude of fluorescence and said shadow length of individual fibers.   
     
     
       17. The apparatus of claim 15 wherein the wavelength of said incident beam of light is about 488 nm and the wavelength of the detected fluorescence is about 574 nm.